4 Sir R. I. Murchison’s Address on the 
For hitherto the order of the geological succession, even as 
seen in the Geological Map of England and Wales or Ireland, 
as approved by Sir Henry De la Beche and his able coadjutors, 
Phillips, Ramsay, Jukes, and others, admit no older sediment 
than the Cambrian of North Wales, whether in its slaty condi- 
tion in Merioneth and Caernarvon or in its more altered condi- 
tion in Anglesea. 
The researches in the Highlands have, however, shown that 
in our own islands, the older palzeozoic rocks, properly so called, 
or those in which the first traces of life have been discovered, 
do repose, as in the broad regions of the Laurentian Mountains of 
Canada, upon a grand stratified crystalline foundation, in whic 
both limestones and iron-ores occur subordinate to gneiss. In 
Scotland, therefore, these earliest gneissic accumulations are now 
to be marked on our maps by the Greek letter alpha, as pre- 
ceding the Roman a, which had been previously applied to the 
lowest known deposits of England, Wales, and Ireland. Though 
we must not dogmatise and affirm that these fundamental de- 
sth were in the pristine state absolutely unfurnished with any 
iving things (for Logan and Sterry Hunt, in Canada, have sug- 
gested that there they indicate traces of the former life), we may 
conclude, that in the highly metamorphosed condition in which 
they are now presented to us in North Western Britain, and as- 
sociated as they are with much granitic and hornblendic matter, 
they are for all purposes of the practical geologist “‘azoic rocks.” 
The Cambrian rocks, or second stage in the ascending order as 
seen reposing on the fundamental gneiss of the North West of 
Scotland, are purple and red sandstones and conglomerates form- 
ing lofty mountains. These resemble to a great extent portions 
of the rocks of the same age which are so well known in the 
Longmynd range of Shropshire, and at Harlech in North Wales, 
and Bray Head in Ireland. 
At Bray Head they have afforded the Oldhamia, possibly an 
Alga, whilst at the Longmynd, in Shropshire, they have yielded 
to the researches of Mr. Salter some worm-tracks and the trace 
of an obscure crustacean. 
The Highland rocks of this age, as well as their equivalents, 
e Huronian rocks of North America, have as yet afforded 
no trace whatever of former life. And yet, such Cambrian 
Tocks are in parts of the Longmynd, and specially in the lofty 
mountains of the North Western Highlands, much less meta- 
morph than many of the crystalline rocks which lie upon 
by Professor Ra , L adopted, at his suggestion, the word “ Laurentian, 
pment to my friend, Sir illiam Logan, who had then worked out the or- 
anada, and mapped it on a stupendous scale. I however, at the 
that, if a British synonym was to have been taken, I 
Lewisian,” from the large island of the Lewis, almost wholly cou- 
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